1. Field of the Invention
The invention relates in general to an image de-interlacing processing apparatus, and more particularly to a motion compensation de-interlacing image processing apparatus and associated method.
2. Description of the Related Art
Contributed by the digital television era, a television can not only receive television broadcasts and allow internet applications such as internet browsing, but a digital television is also able to offer video/audio quality and customization that far surpasses those of a conventional analog television. According to worldwide digital television specifications, television signal formats include progressive and interlaced scanning signal formats, which respectively have their advantages and disadvantages. Most significant advantages of the interlaced scanning signal formats include transmission data amount being relatively small while rendering better sharpness and contrast for dynamic images. Therefore, for situations requiring high-resolution and large-screen televisions and particularly with 1080 scan lines, interlaced scanning requiring less data transmission is more extensively applied to save transmission bandwidth.
Referring to FIG. 1, in interlaced scanning, each frame is divided into an odd field and an even field, with the odd field comprising only pixels of odd lines of the frame and the even field comprising only pixels of even lines of the frame. During transmission, the odd fields and the even fields are alternately transmitted such that the transmitted data amount within unit time is halved. However, image data received at an image receiving end is data of either odd fields or even fields rather than a complete frame, so that de-interlacing is needed to make up pixel data of the odd lines or even lines that are not transmitted to the receiving end at a same time point in order to generate a complete frame to be displayed on an image display apparatus. More specifically, an input odd field comprises only pixel data of 1st, 3rd, 5th, 7th, 9th . . . lines, and an input even field comprises only pixel data of 2nd, 4th, 6th, 8th, 10th . . . lines. Yet, it is necessary that an output image contain progressive frames that comprise pixel data of 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th . . . lines when outputting an image.
Common de-interlacing processing includes spatial de-interlacing and temporal de-interlacing. The spatial de-interlacing utilizes pixels having a same horizontal axis in previous and next lines in the field at a same time point for interpolating a target pixel to be interpolated, generally by interpolating with a pixel value obtained by averaging the previous and next pixels, or interpolating with a pixel value directly selected from either the previous or the next pixel. For example, consider a pixel A in an odd field Fn in FIG. 1 is a target pixel to be interpolated. With spatial de-interlacing, a pixel B at a previous line and a pixel C at a next line are averaged to obtain a pixel value for the pixel A, or one of the pixel B and the pixel C is directly selected as the pixel A. On the other hand, the temporal de-interlacing utilizes pixels at a same position in a previous field and a next field to interpolate a target pixel to be interpolated, by interpolating with a pixel value obtained by averaging the two pixels at a same position in the previous field and the next field. For example, consider again a pixel A in an odd field Fn in FIG. 1 is a target pixel to be interpolated. With temporal de-interlacing, a pixel D and a pixel E respectively at a same position in a previous odd field Fn−1 and a next field Fn+1 are averaged to obtain a pixel value for the pixel A. However, neither spatial de-interlacing nor temporal de-interlacing is capable of interpolating real pixels for dynamic images such that resulting image distortion is incurred. Therefore, the present invention utilizes estimation of motion vectors to accordingly interpolate real pixels to thereby enhance image quality.